The present invention relates to a bending machine for use in bending pipes such as oil pipes and iron bars and the like. More particularly, the invention relates to a bending machine comprising a feed mechanism mounted on a base block for advancing a length of workpiece to a bending section, and a bending assembly including a plurality of rotatable bend dies arranged along a common rotational axis and a plurality of clamp dies movable toward and away from the bend dies, the bend dies and the claim dies being adapted to hold the workpiece therebetween and bend the workpiece by rotating in unison about the rotational axis.
A bending machine as described above which comprises a bending assembly including a plurality of bend dies arranged along a common rotational axis is capable of bending elongate workpieces having varied diameters and bending such workpieces to varied curvatures by selecting suitable bend dies. In order to achieve this, however, the bending assembly and the workpiece must be movable relative to each other in directions on a bending plane of the workpiece and in directions along the rotational axis of the bend dies. According to a known construction, a first actuator for effecting the movements on the bending plane and a second actuator for effecting the movements along the rotational axis of the bend dies are both mounted on the base block. More particularly, the two actuators are provided between the feed mechanism and the base block to move the workpiece on the bending plane and along the rotational axis of the bend dies. However, where the movements on the bending plane is effected by means of the feed mechanism supporting the elongate workpiece, the positional adjustment of the workpiece tends to lack in precision although the movements along the rotational axis may be effected with no problem. Such precision cannot be assured because it is an attempt to control the position of a part of the elongate workpiece adjacent a leading end thereof by moving the feed mechanism which is holding a part of the elongate workpiece adjacent a tail end thereof. A bending operation to bend the workpiece by rotating the bending assembly without accurate positioning of the workpiece in the direction on the bending plane, would result in failure to achieve a desired bend angle.
As a solution to this problem a construction has been proposed as in Japanese Patent Publication No. 59-32410, for example. According to the proposed construction, the first and second actuators are both provided between the bending assembly and the base block. More particularly, a frame carrying the bending assembly is attached to the base block to be movable on the bending plane, and the first actuator is provided between this frame and the base block while the second actuator is provided between the frame and the bending assembly. This construction has the advantage of assuring accurate positioning of the workpiece on the bending plane since the bending assembly is moved on the bending plane. However, the second actuator must be moved together with the bending machine and therefore the devices to be moved are heavy, which gives rise to a new problem of lacking in speedy movement and hence poor working efficiency.